Herðubreið
This beautiful black and white image shows Herðubreið with snow on top and the small top tuff cone is clearly visible. Photograph by Skarphéðinn Þráinsson. Click on imge for larger view.
This beautiful black and white image shows Herðubreið with snow on top and the small top tuff cone is clearly visible. Photograph by Skarphéðinn Þráinsson. Click on imge for larger view.
Herðubreið is a tuya that was deposited during the last glaciation. It is a contender for the title of being the world’s most beautiful volcano; it certainly is the most beautiful tuya volcano. A tuya is also called a table top volcano due to its shape. The surrounding ice shaped the erupting lava and worked as a mold for it giving the characteristic round steep sided shape with the flat top. There is though a slight chance that Herðubreið erupted at the end of glaciation or even after deglaciation; there is after all a small tuff cone on the top. But, largely it is an unaltered tuya.
In 2007 a swarm of 5 300 earthquakes took place at a depth of 14 to 21 kilometers under Upptyppingar volcano, this swarm has after that progressed laterally at a slight upwards angle towards Herðubreiðartögl and Herðubreið. The type of earthquakes was brittle earthquakes as rock fractured from the inrushing magma, or magmatectonic earthquakes of type B.
The persistency of later swarms have given ample signals to track this intrusion as it moved upwards towards the surface and all signs so far has pointed to an area from Herðubreiðartögl to Herðubreið as being the likely ground zero if it pops up in the form of an eruption. There have also been smaller swarms indicating new intrusions into the area, both following the same path and also going more straight up from locations under Herðubreið and Herðubreiðartögl.
Herðubreið and Herðubreiðartögl today
Seismic signals combined with sparse GPS data released from the area seems to suggest that an eruption very well can occur at any time now, the time period could be anything from weeks to years. We will not really know until we see a persistant swarm moving from the current depth of 5km upwards to 2km or less.
During the last few days a slow earthquake swarm has been running at about 5 km depth, the earthquakes were small but rather persistant. During the night a brief spike in activity occurred at about midnight local time and at 05.38 a major earthquake swarm started with the maximum magnitude of M3.2 occurring 11 minutes later.
So far the swarm is counted in about 100 earthquakes and counting. The depth is though still not manually checked by the Icelandic Met Office and might very well be moved towards the 5km depth line, several of the earthquakes during the last week has been set at shallow depth by the automatic system and was later manually corrected to about 5km. Do not be surprised if that will be the case for the earthquakes from this swarm.
It is still too early to say if this is the start of the run up towards an eruption, but to be honest I would not be surprised if it was. We will most likely know in a few days if this is it or just a volcanic teaser.
If the volcano would erupt we would not know how she would behave. The most likely behavior would though be an effusive fissure eruption like the one that happened at Herðubreið around 8 000 years ago.Update
Here is a plot made by Cryphia, in green are all the earthquakes since 1995 coded in green, the earthquakes during the last month is color-coded yellow to blue.
In this plot the earthquake swarm of today form a rather neat dyke intrusion going from 10km depth up to 2km. There is also evidence of deeper quakes following what is likely a deep conduit that is being pressurised. One should though note that the earthquakes used in this plot has as of yet not been manually checked by seismologists.
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link to volcanocafe.wordpress.com]
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